Sexual behavior is of central importance in psychosocial research on HIV and AIDS. Therefore, aspects of sexual behavior, its determinants, and its modification, will be the focus of both the assessment protocols and the intervention protocols in the majority of projects within the Center. The Psychosexual Assessment Core will develop and provide the instruments for the assessment of sexual risk behavior. The Core will also be in charge of the quality control of sexual behavior assessments and will train and monitor sex interviewers throughout the Center. In addition, the Core has significant responsibilities for the analysis of sexual behavior data sets from the previous Center, as well as for the analysis of several sets of sexual data in the new Center. Finally, the Core serves as an information resource and participates in the development of new projects.